Wire rope

ABSTRACT

A wire rope which includes a filler material disposed in the interstices between a core rope and respective outer strands and/or in the gaps between individual outer strands wherein the filler element is placed independently in the respective interstices and gaps or an interstice and an outwardly contiguous strand gap as an independent unit. A reinforcing core is anchored in the filler element at least in the interstices between the core rope and the respective outer strands.

This application is a continuation of application Ser. No. 324,664,filed Nov. 24, 1981, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a filler-laid wire rope.

2. Description of the Prior Art

In the fabrication of a wire core rope, it is known in the art to fillthe gaps between the individual outer strands with a filler materiallike a thermoplastic resin or to impregnate a filler material into allthe gaps and interstices including the gaps between the core rope andthe outer strands as disclosed in U.S. Pat. No. 3,824,777. Suchimpregnated wire ropes possess excellent properties in abrasiveresistance, fatigue strength and loss of wire rope breaking load bystranding and closing, due to the effects of suppressing abrasivecontact of the individual outer strands or of the outer strands with thecore rope and entrapping the lubricant oil impregnated into the corerope and strands. However, the conventional impregnated wire rope whichhas the filler material integrally positioned around its entire outerperiphery has an inherent drawback in that the flexibility of the wirerope as a whole is impaired to a considerable degree. Further, thefiller material is susceptible to cracking and peeling especially whenthe rope is used as a running rope.

SUMMARY OF THE INVENTION

Therefore, the present invention has as its object the provision for awire rope which does not invite deterioration in flexibility andprevents cracking and peeling of the filler material, while retainingthe fundamental effects with regard to the higher abrasive resistanceand fatigue strength and reduction of loss of wire rope breaking load bystranding and closing.

One feature of the wire rope according to the present invention residesin the fact that, in filling a filler material in the intersticesbetween the core rope and the respective outer strands and/or in thegaps between the individual outer strands, a filler element is placedindependently in the respective interstices and gaps or an intersticeand an outwardly contiguous strand gap are treated as an independentunit.

Another feature of the invention resides in the fact that a reinforcingcore is anchored in the filler element at least in the intersticesbetween the core rope and the respective outer strands.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the following detailed description when considered inconnection with the accompanying drawings in which like referencecharacters designate like or corresponding parts through the severalviews and wherein:

FIG. 1 is an enlarged sectional view of a wire rope in accordance with afirst embodiment in the present invention;

FIG. 2 is a fragmentary perspective view of a filler element;

FIG. 3 is a schematic view showing filler elements of differentsectional shapes;

FIG. 4 shows an apparatus for producing the wire rope of the presentinvention;

FIG. 5 is an enlarged sectional view taken along line V--V of FIG. 4;

FIG. 6 is an enlarged view showing a wire rope construction inaccordance with a second embodiment;

FIG. 7 is a fragmentary perspective view of the filler elements used inthe second embodiment;

FIG. 8 is an enlarged sectional view showing a third embodiment of thepresent invention; and

FIG. 9 is a fragmentary perspective view of the filler elements used inthe third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, it is to be understood that the present invention isapplicable to wire ropes in general irrespective of the wire rope core,strand core and fibre core. By way of example, the following descriptionshows a wire rope with a wire rope core, more specifically, IWRC6×Fi(25) JIS Type 14.

Referring to FIG. 1, designated by reference number 1 is a core rope, by2 six outer strands arranged around the outer periphery of core rope 1,and by 3 a filler element which fills independently each one of theinterstices a which are formed between core rope 1 and outer strands 2.Filler element 3 of a thermoplastic resin or the like is formed into acord-like shape substantially of triangular cross-section in conformitywith the interstice a, as shown in FIG. 2, and laid together with corerope 1 and outer strands 2 at the time of closing the rope to fill therespective interstices a independently of each other like outer strands2. In this instance, filler elements 3 are preferably formed slightlylarger than the cross-section of the interstices a. By so doing, fillerelements 3 are securely contacted with core rope 1 and outer strands 2by the closing pressure, enhancing the effects of the filler elementsall the more, namely, the effect of separating core rope 1 and outerstrands 2 from each other and the effect of sealing the lubricant oil(not shown) which is impregnated between core rope 1 and outer strands2.

The outer strands of the wire rope are arranged to have a percentage ofvoids in the range of 2.0-6.0%. The grounds for this definition of thevalue of the percentage of voids h are shown below. ##EQU1##

When a wire rope which has a percentage of voids greater than about 2%is bent on a sheave, it is possible to avoid contacts of the strands onthe inner side (compression side) of the bend. This is the reason whythe minimum value of the percentage of voids h is set at 2.0%. On theother hand, if the percentage of voids h exceeds 6.0%, the core rope isexposed to an external view, lowering the commercial value of the wirerope. In addition, a percentage of voids greater than 6% invariablyrequires reduction in the diameter of the outer strands, making itdifficult to guarantee the standard breaking load. Thus, the maximumvalue of the percentage of voids h is 6.0%. Accordingly, in the presentinvention, the filler elements 3 are laid with a precondition that thepercentage of voids h is 2.0 to 6.0%.

It is preferred to anchor a reinforcing core 4 of a wire of hempcentrally in respective filler elements 3. Reinforcing core 4contributes to strengthen filler elements 3 and to prevent its crackingor peeling especially when in service as a running rope, while improvingthe breaking characteristics of the wire rope as a whole. Further, italso has an effect of preventing the filler element from rupturing,falling or twisting during the closing operation.

In addition to the shapes shown in FIGS. 1 and 2, it is possible to formfiller elements 3 in various other shapes as shown in FIG. 3. Accordingto the present invention, such is formed into a suitable shape whichconforms to the interstice a.

The above-described filler-laid wire rope is fabricated by the methodand apparatus as follows. Referring to FIGS. 4 and 5, indicated byreference number 5 is a feeder for core rope 1, by 6 bobbins for theouter strands 2 and filler elements 3, by 7 a guide plate, by 8 aclosing die, by 9 an oil feed tank, by 10 capstans and by 11 a take-upreel. Guide plate 7 is provided with a core rope passing hole 7a at thecenter thereof, filling passing holes 7b formed in positions radiallyoutward of the core rope passing hole 7a, and outer strand passing holes7c formed in positions radially outward of filler passing holes 7b.Filler passing holes 7b are preferably formed substantially in the sameshape as filler element 3 to guide the latter in a correct posture. Corerope 1 and filler elements 3 which are supplied from feeder 5 andbobbins 6 are passed through respective holes 7a and 7b of guide plate 7and thereby held in predetermined positional relationship before beingintertwisted by closing die 8. The filler-laid wire rope of FIG. 1 isthus produced and taken up on reel 11. Thus, the wire rope of theinvention can be produced easily fundamentally by the conventional wirerope fabricating method and apparatus, maintaining core rope 1, outerstrands 2 and filler elements 3 in predetermined positional relationshipby guide plate 7.

With the wire rope of the invention, it is possible to lessonconsiderably the contact pressure as caused between core rope 1 and therespective outer strands 2 by a dynamic load especially during serviceas a running rope, thereby reducing abrasion and fatigue of core rope 1and outer strands 2 as well as the loss of wire rope breaking load bystranding and closing. Further, filler elements 3 seal in and preventexudation of the lubricant oil which is impregnated into core rope 1 andouter strands 2. Consequently, the abrasive resistance and fatiguestrength of the wire rope as a whole are improved while reducing theloss of wire rope breaking load by stranding and closing. Furthermore,the entrapped lubricant oil lessens the necessity for relubrication whenthe wire rope is in service and has the effect of preventing internalcorrosion over a long period of time.

In addition to the above-mentioned fundamental effects, filler element 3has another advantages in that no possibility exists of impairing theflexibility of the wire rope as a whole since the filler element is laidindependently and thus structurally separately in the respectiveinterstice a. Besides, as mentioned hereinbefore, reinforcing core 4protects the filler element against damage, i.e., rupturing or peeling,to ensure the above-mentioned effects of the filler elements for arelatively long period of time.

Illustrated in FIGS. 6-9 are second and third embodiments of the wirerope according to the present invention. In the wire rope of FIG. 6, inaddition to the filler elements 3 which are laid in the interstices abetween core rope 1 and outer strands 2 in the same manner as in theforegoing embodiment, filler elements 3' of a shape fitting to the outerstrand gaps b (filler elements 3 and 3' are hereinafter referred to as"inner filler element" and "outer filler element", respectively) arelaid independently in the outer strand gaps b. In the wire ropeconstruction of FIG. 8, inner and outer filler elements 3 and 3' whichare formed into an integral body as shown particularly in FIG. 9 arelaid in each interstice a and an outwardly contiguous outer strand gapb, treating the interstice a and the contiguous gap b as an independentunit.

The wire ropes shown in FIGS. 6 and 8 lessens not only the contactpressure between core rope 1 and outer strands 2 but also the contactpressure between the individual outer strands 2, improving the wire ropeas a whole in abrasive resistance, fatique strength and loss of wirerope breaking load by stranding and closing. Particularly, these effectsare manifested more pronouncedly in the wire rope construction of FIG. 8in which the outer strands 2 are completely separated by the bridgeportions of the inner and outer filler elements 3 and 3'. These wireropes also give excellent results in the effect of entrapping thelubricant oil.

The wire rope construction of FIG. 6 provides substantially the sameeffect as in the embodiment of FIG. 8 if inner and outer filler elements3 and 3' are arranged to contact with each other in the radialdirection. In the wire rope constructions of FIG. 6 and 8, the effect ofentrapping the lubricant oil is augmented by contacting the adjacentouter filler elements 3' with each other through circumferentiallyextending film portions in such a manner that the outer peripheries ofouter strands 2 are covered by the contacting film portions. On theother hand, although the reinforcing cores 4 are anchored in both theinner and outer filler elements in these wire rope constructions, theymay be embedded basically only in inner filler elements 3 except for aspecial application or a case where increased effects of the fillerelements are desired.

The foregoing wire ropes are also fabricated by laying the fillerelements concurrently with the outer strands at the time of closing inthe same manner as in the wire rope construction of FIG. 1. Needless tosay, the resulting wire ropes also have the effects unique to thepresent invention, namely, retaining flexibility and preventing crackingor peeling of the filler elements, similarly to the wire ropeconstruction of FIG. 1.

In the above-described concurrent filler-laying method which has beenemployed for the fabrication of the wire rope of the invention, thefiller elements are laid in simultaneously with the closing operation sothat there is no need for providing a separate filler-laying stage inthe fabrication process, thus ensuring high production efficiency of therope. The method also has advantages over the conventional coatingmethod since it does not require the preheating treatment of the ropeprior to impregnation of the filler material nor equipment like anextruder. The low equipment cost, coupled with the high productivity ofthe rope, permits realization of a material cost reduction of the wirerope. In view of these points, the simultaneous filler-laying method isconsidered to be the most advantageous and suitable method for thefabrication of the wire rope of the present invention and thus to be thesole method which is conceivable for actual application. However, anyother method may be employed as long as the filler elements can be laidin the same manner.

The following experiments more particularly illustrate the fatiguestrength and other properties of the wire rope according to the presentinvention.

EXPERIMENT 1

The following wire rope specimens of IWRC 6×Fi(25) 16 mm JIS Type 14were subjected to a repeated bending test.

(i) A black wire rope;

(ii) A wire rope construction of FIG. 1 according to the invention; and

(iii) A conventional wire rope having interstices and gaps completelyand integrally impregnated and filled with a thermoplastic resin.

In the test, a pair of testing sheaves were positioned between a drivesheave and a tension sheave, and specimens (i) to (iii) were passed inS-shape through the testing sheaves, fixing their opposite ends to thedrive and tension sheaves through auxiliary ropes. A horizontal tensileload was applied to the tension sheave during repeated bending testsunder the following conditions.

Rope diameter d (mm): 16

Testing sheave pitch diameter

D (mm): 256

D/d ratio: 16

Testing load (kg): 1190

Nominal breaking load of test

wire rope (kg): 11900

Safety factor: 10

Sheave arrangement: S-shape

The test results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                  Number of repeated bendings (times)                                             Initial wire                                                                             10% wire breaking                                      Specimens   breaking   (terminal point of test)                               ______________________________________                                        (i)          8500      17000                                                  (ii)        12500      26500                                                  (iii)       13000      27500                                                  ______________________________________                                    

EXPERIMENT 2

The following wire rope specimens of IWRC 6×Fi(29) 44 mm were tested forflexibility, increase in diameter and loss of wire rope breaking load bystranding and closing. The test results are shown in Table 2.

(i) A black wire rope;

(ii) A wire rope construction of FIG. 1 according to the invention; and

(iii) A conventional wire rope having interstices and gaps completelyand integrally impregnated and filled with a thermoplastic resin.

                  TABLE 2                                                         ______________________________________                                                                       Loss of                                        Flexi-      Rope diameter      breaking                                               bility  Diameter   Increment load                                     Specimens                                                                             %       mm         %         %                                        ______________________________________                                        (i)     100     44.80      0         18.1˜23.1                          (ii)    95f100  45.46˜45.58                                                                        +1.47˜+1.74                                                                       14.1˜18.1                          (iii)   70f75   46.26˜46.38                                                                        +3.26˜+3.53                                                                       14.5˜19.0                          ______________________________________                                    

The flexibility is expressed by an index number based on 100% of theblack rope (speciman (i)), and the loss of wire breaking load bystranding and closing is expressed by: ##EQU2##

The results of Experiments 1 and 2 show that the wire rope of thepresent invention is almost comparable to the completely impregnatedwire rope with regard to the repeated bending strength in spite of thefact that the tested specimen was of the construction of FIG. 1 with thefiller elements laid only in the inner interstices, and excels thelatter in the flexibility and loss of wire rope breaking load as well asthe increment in diameter.

It will be appreciated from the foregoing description that the wire ropeof the present invention retains the improved properties of theimpregnated wire rope in abrasive resistance, fatigue strength and lossof wire rope breaking load by stranding and closing, without impairingthe flexibility of the wire rope, while preventing cracking and peelingof the filler material, and thus has an extremely high practical usecharacteristic.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by letters patent ofthe United States is:
 1. A wire rope comprising:a core rope; a pluralityof outer strands, including outermost strands, laid on the circumferenceof said core rope, said outermost strands having gaps formedtherebetween and forming a plurality of first interstices between saidcore rope and said respective outermost strands and a plurality ofsecond interstices formed between said outermost strands at positionsradially outside of said gaps; means for maintaining flexibility of saidrope without cracking and peeling, said means for maintaining comprisinga flexible filler element of a thermoplastic material formed as anintegral body independently disposed in each of said first intersticesformed between said core rope and said outermost strands, and in each ofsaid gaps and second interstices between the individual outer strands,each said filler element being preformed with a shape corresponding tothat of an interstice in which said filler element is disposed; and areinforcing core embedded in at least said filler element disposed in arespective one of said first and second interstices.
 2. A wire ropecomprising:a core rope; a plurality of outer strands, includingoutermost strands, laid on the circumference of said core rope, saidoutermost strands having radially outwardly extending continguous gapsformed therebetween and forming a plurality of first interstices betweensaid core rope and said respective outermost strands and a plurality ofsecond interstices formed between said outermost strands at positionsradially outside of said gaps; and means for maintaining flexibility ofsaid rope without cracking and peeling, said means for maintainingcomprising a filler element of a thermoplastic material formed as anintegral body disposed in the first interstices formed between said corerope and the respective outermost strands, in the radially outwardlyextending contiguous gaps between the individual outermost strands andin said second interstices, wherein corresponding ones of said first andsecond interstices and a radially outwardly extending contiguous gaptogether comprise a single independent unit, each said filler elementbeing preformed with a shape corresponding to that of an independentunit in which said filler element is disposed, wherein said fillerelement further comprises a reinforcing core embedded therein at leastin a portion located within a respective one of said first and secondinterstices.